add comments

Lab_1/TwoSensorsAAR.c

@@ -9,8 +9,8 @@ float NISTmilliVoltsToDegCKtype(float tcEMFmV);  // returns temp in degC assumin
 
 float adc_to_voltage(float v_ref, int n_adc);
 float kelvin_to_c(float k);
-float resistance_to_temperature(float r);
-float voltage_to_resistance(float v);
+float resistance_to_thermistor_temperature(float r);
+float voltage_to_thermistor_resistance(float v);
 float voltage_to_erc(float v);
 
 int main()
@@ -23,12 +23,12 @@ int main()
 	scanf("%d %d", &thermistor_val, &thermocouple_val);
 
 	// Calculate thermistor temperature in degrees C ( Part b, i,ii,iii & v)
-	thermistor_temp = kelvin_to_c(resistance_to_temperature(voltage_to_resistance(adc_to_voltage(v_ref, thermistor_val))));
+	thermistor_temp = kelvin_to_c(resistance_to_thermistor_temperature(voltage_to_thermistor_resistance(adc_to_voltage(v_ref, thermistor_val))));
 
 	// Calculate thermocouple temperature in degrees C ( Part c, i - iv)
 	e_rc = 1000*voltage_to_erc(adc_to_voltage(v_ref, thermocouple_val)); // convert to millivolts
-	e_comp = NISTdegCtoMilliVoltsKtype(thermistor_temp);
-	thermocouple_temp = NISTmilliVoltsToDegCKtype(e_rc + e_comp);
+	e_comp = NISTdegCtoMilliVoltsKtype(thermistor_temp); // eqn (6) lab prep sheet
+	thermocouple_temp = NISTmilliVoltsToDegCKtype(e_rc + e_comp); // eqn (7) lab prep sheet
 
 
 	// Output results
@@ -42,7 +42,7 @@ int main()
 /* Write a function here to convert ADC value to voltages. (Part a, equation 1)
 Call it from the main() function above */
 float adc_to_voltage(float v_ref, int n_adc) {
-	return (float)n_adc*v_ref/1024.0;
+	return (float)n_adc*v_ref/1024.0; // eqn (1) lab prep sheet
 }
 
 
@@ -54,23 +54,29 @@ float kelvin_to_c(float k) {
 }
 
 
-float resistance_to_temperature(float r) {
+// Convert Resistance (Ohms) to Temperature (Kelvin) (for thermistor)
+float resistance_to_thermistor_temperature(float r) {
 	// Define Thermistor constants
-	float t_0 = 298.15;
-	float r_0 = 10000;
-	float b = 3975;
+	float t_0 = 298.15; // Kelvin
+	float r_0 = 10000; // Ohms
+	float b = 3975; // Kelvin
 
-	return 1.0 / ( (1.0/t_0) + (1.0/b)*log(r/r_0));
+	return 1.0 / ( (1.0/t_0) + (1.0/b)*log(r/r_0)); // eqn (3) lab prep sheet
 }
 
 
-float voltage_to_resistance(float v) {
-	return 1000*((10.0*3.3/v)-10.0);
+// Convert Voltage (Volts) to Resistance (Ohms)
+float voltage_to_thermistor_resistance(float v) {
+	float pull_down_resistance = 10; // kOhms
+	float v_hi = 3.3; // Volts
+
+	return 1000*((pull_down_resistance*v_hi/v)-10.0); // eqn (4) lab prep sheet
 }
 
 
+// Convert Voltage to E_RC
 float voltage_to_erc(float v) {
-	return (v-0.35)/54.4;
+	return (v-0.35)/54.4; // eqn (5) lab prep sheet
 }